Section 230 doesn't say anything about publishers. That was entirely made up by chronically online arguers.

What it does say is you aren't liable for something someone else wrote.

It doesn't create liability for things not covered by it.

Guess who decides the order and contents of Facebook feeds? Facebook does. So they wouldn't be liable for someone writing a post saying "gas the jews" but they would still be liable for choosing to show it at the top of everyone's front page, if that was a choice, because the front page was choice-based rather than chronological.